3beta-hydroxy-5alpha-cardenolides and-bufadienolides and process for their manufacture

ABSTRACT

A PROCESS FOR THE MANUFACTURE OF 3B-HYDROXY-5A-CARDENOLIDES AND 3B-HYDROXY-5A-BUTADIENOLIDES OF THE GENERAL FORMULA I   10-R2,11-R6,12-R5,14-R3,15-R4,17-R1-ESTRAN-3-OL   IN WHICH R1 REPRESENTS THE BUTENOLIDE RING OR THE A-OYRONE RING   5-(O=)-2,5-DIHYDROFUR-3-YL OR   6-(O=)-6H-PYRAN-3-YL   R2 REPRESENTS CH3, CH2OH OR -CH2-OOC-CH3; R3 REPRESENTS A HYDROGEN ATOM IN A- OR B-POSITION OR A HYDROXY GROUP WHICH MAY BE ESTERIFIED; R4 REPRESENTS A HYDROGEN ATOM; OR R3 AND R4 TOGETHER REPRESENT A 14(15)DOUBLE BOND OR AN EPOXY GROUP IN 14,15B- OR 14,15A-POSITION; R5 AND R6 EACH REPRESENTS A HYDROGEN ATOM OR A HYDROXY GROUP IN A- OR B-POSITION WHICH MAY BE ESTERIFIED, WHICH PROCESS COMPRISES REDUCING 3-OXO-4(5)-DEHYDRO-CARDENOLIDES OR -BUFADIENOLIDES OF THE GENERAL FORMULA   10-R2,11-R6,12-R5,14-R3,15-R4,17-R1-ESTR-4-EN-3-ONE   IN WHICH R1, R2, R3, R4, R5 AND R6 HAVE THE MEANINGS GIVEN ABOVE AND R2 MAY ADDITIONALLY REPRESENT THE ALDEHYDE GROUP CHO, AND R5 AND R6 MAY REPRESENT THE OXO GROUP, WITH ORGANOMETALLIC REDUCING AGENTS OR REDUCING AGENTS HAVING A SIMILAR EFFECT, THE REDUCING POWER OF WHICH ARE SUPERIOR TO THAT OF SODIUM BORON HYDRIDE, IN THE PRESENCE OF ORGANIC NITROGEN BASES AT TEMPERATURES OF FROM -30* TO +60*C. CARDIOACTIVE 3B-HYDROXY-5A-CARDENOLIDES AND BUFADIENOLIDES OBTAINED BY THIS PROCESS.

I Claims priority, aplpglication Germany, July 7, 1970,

P Patented I V hyde group CH0, and R and R may represent the x0 3,812,106

I V group, with organometallic reducing agents or reducing 3/3 HYDR OXY Sa-CARD'ENOLIDES AND agents having a similar eifect, the reducing power of which -BUF I AND PROCESS FOR are superior to that of sodium boron hydride, in the pres- THEIR MANUFACTURE 1 ence of organic nitrogen bases at temperatures of from .Ulrrch Stache, Hofherm, Taunus, Kurt Radscheit, Kelkto 0 v heim Taun'us Werner Fritsch Neuenhain Taunus and wenier Ha Hoiheim Tmmus, cermny assignors Card1oact1ve 3;? hydroxy 50c cardenolides and bufadle to Farbwerke 'Hoechst Aktiengesellschaft vormals nolides Qbtained b t P Meister Lucius & Bruning, Frankfurt am Main, Germany I No Drawing. Filed July 6, 1971, Ser. No. 160,220

The present invention relates to 3 fi-hydroxy-5u-cardenolides and 3B-hydroxy-Sa-bufadienolides and to a process 33 5993 for their manufacture. 7 Int CL 7 73 /02, 73 04 7 It is already known that Sfi-hydroxy-5a-cardenolides US. Cl. 260-23957 2 Claims can be prepared by reducing 3-oxo5a-cardeno1ides sat- I 15 urated in 4(5)-position with organometallic reducing agents, for example sodium boron hydride or lithium ABSTRACT F THE DISCLOSURE tributoxy aluminum hydride, in solvents which do not con- A process for the manufacture of 3/3-hydr0xy-5a-car tain organic bases, without reducing the 17fl-butenolide denolides and 3}3-hydroxy-5a-bufadienolides of the genring which is sensitive to reducing agents (Chem. Ber. 'eral FormulaI y 2 88, p. 686 (1955); Liebigs AnnpChemie 726, p 136 j Cm (1969)). Reductions of 3-oxo-4(5)-dehydro-cardenolides or -bufadienolides, which are carried out in a correspond- R6 ing manner, do not yield the 3B-hydroxy-5u-analogs saturated in 4(5)-position but yield the 3 3-hydroxy-4(5)- 2 dehydro-cardenolides or -bufadienolides unsaturated in p 4(5)-position (Liebigs Ann. Chemie 727, p. 110 (1969). MR Tetrahedron Letters, p. 3033 (1969)).

A process, according to which )3-hydIOXy-5a-CE1Y- denolides or -bufadienolides are prepared in a single reaction step from 3-oxo-4(5)-dehydro-cardenolides or -bufadienolides, has not yet been disclosed. Although it I is known that certain 3-oxo-4(5)-dehydro-steroids of the I pregnane and androstane series, for example progesterone, in which R represents the butenolide ring or the ot-pyrone and 11fi h d A-1 d t 3 17 di can be T1118 p, V 3 duced in one step to the corresponding 3B-hydroxy-5a- 0 steroids saturated in 4(5)-position with sodium boron 0 hydride in the presence of pyridine (Tetrahedron Letters '15, p. 193 (1961)), the corresponding reaction is useless 40 in the case of 21-fiuoro-progesterone. The attempt to reduce' the corresponding 3-oxo-4(5)-dehydro-cardenolides v and bufadienolides in the same manner with sodium boron 0 hydride in pyridine to the corresponding 3fl-hydroxy-5acompounds has neither been successful.

The present invention now provides a process for the manufacture of 3fl-hydroxy-5a-cardenolides and -bufadienolides of the general formula l[ llllll NIH-L R represents CH CH OH or CH1 0 cnzoiicm; 1

R represents-a hydrogen atom in aor B-position or a hydroxy group which may be esterified; R represents a hydrogen atom; or R and R together represent a 14( 15 double bond or an epoxy group in 14,155 or 14,15a-position; R and R each represents a hydrogen atom or a vhydroxy group in a-or B-position which maybe esterified, which process comprises reducing 3-oxo-4(5)-dehydro-cardenolides or -bufadienolides of the general formula in which R represents the butenolide ring or the a-pyrone CH: 7 ring M-R| E in which R R R R R and R have the meanings given above and R; may additionally represent the alde- IIHII- R represents a hydrogen atom in aor St-position or a hydroxy group which may be esterified; R represents a hydrogen atom; or R and R together represent a 14(15)-double bond or epoxy group in 14,155- or 14,150 position; R and R each represents a hydrogen atom hydroxy group in aor fi-position which may be esterified or an oxo group. The process comprises reducing 3-oxo- 4(5)-dehydro-cardenolides or -bufadienolides of the general formula in which 'R R R R R and R have the meanings given above and R may additionally represent the aldehyde group CH0, and R and R may represent the oxo group, with organometallic reducing agents or reducing agents having a similar efiect, the reducing power of which is superior to that of sodium boron hydride, in the presence of organic nitrogen bases at temperatures of from 30 to +60 C. I

In this process, it is surprising that the organometallic reducing agents having a superior reducing power do generally not affect the butenolide ring of cardenolides or the a-pyrone ring of bufadienolides, both in l7-position, which rings are necessary for a fully cardiac activity. of the active ingredients. It must be borne in mind that the a-pyrone ring of bufadienolides is even less stable towards reducing agents than the butenolides ring of cardenolides. Furthermore, hydroxy groups, for example in 11-, 12-, 14- or 19-position, which may alsobe. esterified, isolated double bonds, for example in 14('15)-position, or epoxy groups, for example in l4(l5)position, may be present without being altered under the reaction conditions. A possible aldehyde group in l9-position is generally reduced at the same time to the 19-alcohol group under the conditions of the present'process. In the same manner, oxo groups which may be present in other positions, for example in 11- or 12-position, are also reduced to the corresponding alcohol groups.

As starting substances there may, for example be mentioned the following 3 oxo 4(5 )-dehydro-cardeno1ides and bufadienolides which lead to the corresponding 35- hydroxy-5u-cardenolides or -bufadienolides.

3-oxo-14u-carda-4,20( 22) -dienolide 3 ,B-hydroxy-S a,

' 14-card-20 (-22) -endolide 3-oxo-carda-4,14,20(22)-trienolide (-=14( l5 -anhydrocanarigenone 3 fi-hydroxy-Sa-card- 14,20(22) dienolide 14( IS-anhydro-uzarigenin) 3-oxo-14-15/8-oxido-carda-4,20(22) -dienolide- 318- hydroxy-14, 15,B-oxido-5a-card-20( 22) -enolide CarnarigenoneeUzarigehin 4 5 -anhydro k-stroph anthidone coroglaucigenin 12fl-hydroxy-carnarigenonesyriogen'm -1 1fi-hydroxy-canarigenonemallogenin 3-oxol4a-bufa-4,20, 22-trienolide- .3 3-hydroxy-5 a- 14a-bufa20,22-dienolide 3-oxo-bufa-4, 14,20, 22-tetraenolide 14 (1 5 -anhydroscillarenone) 3 fi-hydrOxy-Sa-bufa-14,20,22-trienolide (=14(15)anhydro-5a-bufalin) 3-oxo-14,'15;}8-oxido-bufa-4,20,22-trienolide- 318-hydroxy-14,1Sfl-oxido-Sa-bui-ZO,ZZ-dienolide 3-oxo-14,15 u-oxido-bufa-4-20,22-trienolide 3B-hy-" droxy-14,lSa-oxido-Sa-bufa-ZO,22-dienolide Scillarenone S a-bufalin 3-dehydro-scilliglaucosidine and 3-dehydro-scilliglaucosidin-ol- Bovogenol A p 12B-hydroxy-scillarenone l2fi-hydroxy- 5a -bufalin The organo-metallicf' reducing agents preferably used are agents having a reducing power superior to that of sodium boron h'ydride,for example sodium trimethoxy boron hydride, lithium boron hydride, calcium boron hydride, strontium boron hydride, barium boron hydride, aluminum boron hydride, lithium trimethoxy boron hydride, magnesium boron hydride, zinc boron hydride, aluminum hydride, sodium aluminum hydride, magnesium aluminum hydride, lithium aluminum hydride, and lithium trimeth'ox'y aluminum hydride, as well as diborane, pyridine-borane, ethane-1,2-diamine borane and monoor bisalkyl boranes, such as, for example, mono- (-3-methyl-2-butyl) borane. I 1

As inert solvents there may be used: Tetrahydrofuran, dioxan', diethyl ether, dimethylformamide acetonitrile and diglyme.

As organic bases there may be preferably mentioned according to the process of the invention: Pyridine, quinoline, ethylenediamine, dirnethyl-aniline, collidine, triethylamine, ethylamine, ethanol-amine, N-methyl-ethanolamine and N-dimethyl-ethanol-amine.

According to the invention, for example, the 3-oxo- (5)-dehydro-cardenolide or -bufadienolide is dissolved in one of above organic bases, preferably pyridine, and one of the above inert solvents may be added, if necessary. Subsequently, one of the above organometallic reducing agents is added in a 1 to IOO-fold molar excess,

preferably a 5 to 40-fold molar excess, to the vigorously stirred solution, if necessary while cooling and dissipating the reaction heat produced. Alternatively, the organometallic reducing agent may be suspended or dissolved in one of the above organic bases, if necessary with addition of one of the above solvents, and then the steroid is added.

The reaction mixture is then stirred for 1 to 72 hours,

preferably for 2 to 10 hours, at temperatures of from -20 to +30 C. When the reaction is complete, the excess of organo-metallic reagent is destroyed in the usual manner and the product is worked up in the usual manner by extraction with a suitable organic extracting agent.

After elimination of the extracting agent by distillation, the products of the invention are generally obtained in a gram.

still impure and crude state. By the usual preparative chromatography on silicagel or aluminum oxide, the products of the invention can'be obtained as compounds that are uniform according to the thin-layer chromato- The products of the invention have valuable-pharma+ cological properties, for example highly cardiotonic (positively inotropic) action, which is measured by potassium secretion or by a test on the atrium of an isolated heart of a Guinea pig as well as spasmolytic or diuretic prop: erties. i a t f Generally, the 3fl-hydroxy-sascardenolideshave a relatively weak, positively inotropic action, but they develop a strong spasmolytic action on non-striated muscles. In

is from about 0.1 to 1 mg. per dosage unit.

The compounds of the invention are especially administered per os in the form of tablets, capsules or dragcs, optionally in admixture or conjunction with the pharmaceutically suitable carriers, such as starch, lactose, tragacanth, magnesium stearate or talc. They may also be injected intravenously, a physiological sodium chloride solution or water serving as the solvent.

The following Examples serve to illustrate the invention.

EXAMPLE 1 p (a) 200 mg. of lithium boron hydride were added portionwise at 22 C., while stirring, to a solution of 1.06 g. of 3-oxo-14a-carda-4,20(22)-dienolide in 14 ml. of absolute pyridine. After stirring had been continued for 6 hours at C., the reaction mixture was cautiously poured into 100 ml. of semisaturated aqueous sodium chloride solution. The mixture was extracted with methylene chlo-;

ride and the extracts were treated with 0.2-0.1 N aqueous hydrochloric acid. Theproduct was then washed ,with water and dried and the solvents were distilled-01f in vacuo. The remaining oil (1.02 g.) was then chromatographedon silica gel [0.05-0.2 mm. Merck,-colnmn size 3 x 25 cm.]. The product was first eluted with 950 ml. of methylene chloride and then with 500 ml. of methylene chloride -+1% of methanoL-After elimination of the solvents by distillation, 634mg. of asolid' residue were obtained from the last chromatography fraction (500'ml.).' After recrystallization from acetone/diisopropyl ether, 485 mg. of 3/3-hydroxy a,14a-card-20(22)-cnolide were obtained, M.P. 210-212 C. Typical infrared bands (in KBr): 3450, 3120, 1780, 1745, 1730, 1620 cmr ('b) When, instead of lithium boron hydride, 80 mg. of diborane were slowly fed at 0 C. to the above reaction solution and the reaction was treated and worked up in a manner analogous to that disclosed in Example 1(a), the same product having the same characteristics as in Example 1(a) was obtained.

EXAMPLE 2 In a manner analogous to that disclosed in Example 1(a), 1.06 g. of 3-oxo-carda-4,14,20(22)-trienolide were reacted and worked up. After purification by chromatography, 3B-hydroxy-5u-carda-14,20(22)-dienolide .was obtained, M.P. 251-253 C. Typical infraredbands (in KBr): 3440, 3100, 3055, 1795 (shoulder), 1775,1750 (shoulder), 1720, 1620 cmr i EXAMPLE3 A solution of 1.2 g. of 3-oxo-14 3-hydroxy-carda-4,20

(22)-'dienolide (=canarigenone) in '17 ml. :of'ab'solut" pyridine was treated for'7 hours at 0 C. with 480mg. of

uzarigenin was obtained, M.P. 247-249' C. The 'character-- lithium boron hydride and worked up as disclosed in Ex-. ample 1(a). After purification by chromatography,

istics of the ultraviolet and infrared spectra werecomplete ly -indentical with the corresponding values'of an authentic comparative preparation. I v i "EXAMPLE4 I EXAMPLE 5 A solution of 750 mg. of. 3-oxo-bufa-4,14,20,22-tetraenolide =14-anhydro-scillarenone) in 15 ml. of absolute pyridine was treated for 7 hours at 0 C. with 250 mg. of lithium boron hydride and worked up as disclosed in Example 1(a). After purification by chromatography, crys- 6 tallized 3 3. -hydroxy-5a-bufa-14,20,22-trienolide (=14-anhydro-'Sd-bufalin) was obtained from the precipitated oily residue of thelast chromatography fraction after digesting with-ether. Typical infrared bands (in KBr): 3490, 3450 (shoulder),.1740, 1715, 1630, 1530 cm.-

EXAMPLE 6 Sa-bufalin (a) A solution of 750 mg. of scillarenone in 15. ml. of absolute pyridine was treated for 7 hours at 0 C. with 450 mg. of lithium boron hydride and worked up as disclosed in Example 1(a). After purification by chromatography on silica gel (as in Example 1(a), except that 2%, insteadof 1%, of methanol were added as eluant to thechloroform) and after elimination of the eluant, CHCL 'CH OH=98:2, a crystallized residue was obtainedwhich was recrystallized from acetone/ether. 3p, 14fl-dihydroxy 5a-bufa-20,22 dienolide (Sa-bufaIin) was obtained, M.P. 230-234 C.

(b) ..(The following reaction steps starting from 14- anhydro-5u-bufalin and yielding 5u-bufalin were carried out in exactly the same manner as disclosed in Belgian Pat. No. 732,210.)

-A mixed anhydride of formic acid and acetic acid was slowly added dropwise, while intensely stirring and cooling the reactor, to a solution of 370 mg. of the 14-anhydro-5 t-bufalin'obtained according to Example 5 in 1.9 ml. of absolute pyridine. (Preparation of the anhydride: 1.3-3- ml. of --acetic anhydride were slowly added dropwise, while cooling with ice, to 5.5 ml. of a formic acid. The mixture was then allowed to react for 15 minutes at 50? (3., and then cooled to +5 C. The mixed anhydride thus obtained was used at once.)

During the dropwise addition of the anhydride reagent the temperature in the reaction mixture did not exceed 15 C. After the addition, the reaction mixture was stirred for another hour at 23 C. and then mixed with about 100 ml. of water, whereupon a crystalline precipitate separated. The precipitate obtained was suction-filtered, washed with water and dried in vacuo. 353 mg. of 14- anhydro-5u-bufalin-3-formiate were obtained. Typical infrared bands (in KBr).: 1 745, 1720,. 1635,: 1535, 1175 cm.- (no more hydroxyl bands present). The product.

11- 'm1. of dioxanwas combined while cooling with ice and stirring with a 'mixtureof glacial acetic acid and 2.0

ml. of water. Them 200 mg. of freshly recrystallized-N,N-' dibromobenzene sulfonamide were introduced into the carefully stirred mixture. After stirring for 1 hour, while cooling with ice, the mixture was poured onto 100 ml. of .icewater. After extraction" with methylene chloride,

the extracts we'rewashedwith water and dried over -so-'- dium sulfate. After elimination of the solvents by distillation, a foam was obtained which'gave a strongly positive Beilstein test for halogen and was immediately used for the subsequent reaction step. For this purpose, the crude 15a-14fi-bromohydrin obtained was dissolved in 20 ml. of methylene chloride and this solution was mixed while stirring with a suspension of a nickel catalyst obtained from 13 g. of moist Raney nickel as hereinafter disclosed. After stirring with for 3.5 hours at 23 C. the catalyst was separated by filtration. The solvent 'was eliminated by distillation and the dry residue obtained (205 mg.) was dissolved in 4 ml. of absolute methanol for hydrolysis of the 3-formate group. After the addition of 1.8 ml. of. absolute methanol saturated with ammonia gas, the "re action mixture was allowed to stand for 18 hours at 0 C. Subsequently, it was concentrated in vacuo until it was dry. The solid residue was taken up in about 30 ml. of methylene chloride. The solution was washed twice 7 Y a with water, dried over sodium sulfate, and methylene chloride was distilled off in vacuo. The residue obtained was chromatographed on silica gel Merck (column size 3 x 21 cm.). It was first eluated with 2500 ml. of chloroform and then with 1000 ml. of chloroform/ methanol (98:2). After elimination of the solvents by distillation from the latter eluate, a crystallized residue was obtained which was recrystallized from acetone/ether. Sa-bulfalin was obtained, M.P. 231-235 C; no depression with the Sa-bufalin prepared according to Example 6(b). The infrared spectra were also indentical.

Preparation of the catalyst 13 g. of water-moist Raney nickel were carefully whirled about for some seconds three times with 130 ml. of water each, and the supernatant water was decanted after the Raney nickel had deposited. The same operation was repeated three times using 20 ml. of methanol each time. After the decanting of the last supernatant methanol, 20 g. of a methanol-moist Raney 'nickel paste were obtained which had a volume of about 10 ml., corresponding to an amount of about 6.8 g. of dry Raney nickel.

EXAMPLE 7 In a manner analogous to Example -1 (a), 1.1 g. of 3- oxo-14a-bufa-4,20,22-trienolide (prepared in known manner by the usual Oppenauer oxidation from 3p-hydroxy- 14a-bufa-5,20,22-trienolide) were reacted in 14 ml. of pyridine with 200 mg. of lithium boron hydride for 6 hours at C. and worked up. After chromatography on silica gel, 312 mg. of 3B-hydroxy-5a, 14a-bufa-20,22- dienolide were obtained after digesting with diisopropyl ether, M.P. 241-247 C. Typical infrared bands (in KBr): 3470, 1740, 1715, 1630, 1530 cmr EXAMPLE 8 In a manner analogous to Example 1(a) 550 mg. of 3-oxo-14,15,8-oxido-bufa-4,20,22-trieno1ide in 7 ml. of pyridine were reacted with 100 mg. of lithium boron hydried for 6 hours at 0 C. and the reaction product was worked up. After chromatography on silica gel, S S-hydroxy-14,lB-oxido 5a bufa-20,22-dienolide was obtained after digesting with diisopropyl ether, M.P. 248- 253 C."

" EXAMPLE 9 R taken alone, is aor fl-hydrogen or hydroxy,.which may be esterified; 1

R ,.taken alone, is hydrogen;

R and R taken together, area 14(15 )-double bond or R is hydrogen or oz or p-hydroxy, which may be esteri- R, is hydrogen or aor p-hydroxy, which may be esterified;

which'method comprises contacting a 3-oxo-4(5)-dehydro-cardenolide or 3Ox0-4(5)-dehydro-bufadienolide of the formula wherein .R R R R R and R, have their earlier meanings; R, may additionally be CHO; and R and R, may additionally be oxo, in an organic nitrogen base at a temperature from 30 C. to 60 C., with an organometallic reducing agent having a reducing power greater than that of sodium boron hydride, said agent being selected from the group consisting of sodium trimethoxy boron hydride, lithium boron' hydride, calcium boron'hydride, strontium boron hydride, barium boron hydride,

aluminum boron hydride, lithium trimethoxy boron hydride, magnesium boron hydride, zinc boron hydride, aluminum hydride, sodium aluminum hydride, magnesium aluminum hydride, lithium aluminum hydride, lithium trimethoxy aluminum hydride, diborane, pyridine-diborane, 'ethane-LZ-diamine borane, and monoand bisalkyl boranes.

' 2. 3p-hydroxy-14,15p-oxido-5a-bufa-20,22-dienolide.

. References Cited "UNITED STATES PATENTS 13,682,895 7 8/1972 Pettit et a1. zed-239.57

I OTHER REFERENCES l I I Pettit et al.: Canadian Journal of Chemistry (1969), V01. 47, PP- 2511-2512. A

"Pettit et -al.: Jour. of Org. Chem. (May 1970 pp. ii .1 l ELBERT L. ROBERTS, Primary Examiner 1 us. 01. x.R.-' 

